1. Field of the Invention
The present invention relates to an image forming apparatus. More particularly, the present invention relates to a rotary roller structure and a fuser of an image forming apparatus employing the rotary roller structure.
2. Description of the Related Art
A rotary roller structure transfers a sheet-shaped object, for example, a sheet of paper, with a pair of rollers that are engaged with each other and rotate. The rollers are engaged with each other at a predetermined pressure in the lengthwise direction of the rollers. The pressure should be constant during the rotation of the rollers. When any of the rollers has an elastic layer, the size of a nip formed by the compression of the elastic layer should be constant in the lengthwise direction during rotation of the rollers.
A rotary roller structure may be employed in a fuser of an electrophotographic image forming apparatus having a heat roller and press roller. If the pressure and nip of the heat roller and the press roller are not constant, a recording medium may be skewed. Furthermore, the heat and pressure transferred to the recording medium may become unstable so that fusing performance deteriorates. The imbalance of the pressure and nip of the two rollers is caused by various factors such as processing errors or roundness errors.
Accordingly, there is a need for an improved rotary roller structure which maintains a constant pressure and a constant nip.